U.S. Pat. No. 4,281,092, granted July 28, 1981 to Breazeale, discloses vulcanizable perfluoroelastomer polymers comprising copolymerized units of
(a) 53-79.8 mole percent tetrafluoroethylene, PA1 (b) 20-45 mole percent perfluoromethyl perfluorovinyl ether, and PA1 (c) 0.2-2 mole percent of a cure-site monomer of the formula: ##STR1## where n=1-4 and PA1 x=1-2. PA1 (a) 53-79.8 mole percent tetrafluoroethylene, PA1 (b) 20-45 mole percent perfluoromethyl perfluorovinyl ether, and PA1 (c) 0.2-2 mole percent of a cure-site monomer of the formula: ##STR3## where n=1-4 and x=1-2. The vulcanizing agent is a compound selected from the group consisting of bis(aminophenols) of the formula ##STR4## and tetraamines of the formula ##STR5## where A is SO.sub.2, O, CO, alkyl of 1-6 carbon atoms, perfluoroalkyl of 1-10 carbon atoms, or a carbon-carbon bond linking the two aromatic rings. The amino and hydroxyl groups in formula (2), above, are interchangeably in the meta and para positions with respect to the group A. PA1 (a) 4,4'-[2,2,2-trifluoro-1-(trifluoromethyl)-ethylidene]bis(2-aminophenol), PA1 (b) 4,4'-sulfonylbis(2-aminophenol), PA1 (c) 3,3'-diaminobenzidene, and PA1 (d) 3,3',4,4'-tetraaminobenzophenone.
These polymers are the same as are used in the method and composition of the present invention. Breazeale discloses vulcanization of these polymers with substances known to promote the formation of trazine rings by trimerization of nitriles, e.g. organometallic compounds of arsenic, antimony and tin and certain metal oxides. The preferred vulcanizing agent is disclosed to be tetraphenyltin. Use of the present invention, rather than vulcanizing with tetraphenyltin, gives finished product having higher hydrolytic stability and higher thermal stability. In addition, the method and composition of the present invention provides a convenient alternative to the curing system heretofore recommended for the polymers disclosed by Breazeale.
U.S. Pat. No. 3,467,638, granted Sept. 16, 1969 to Pattison, discloses certain vulcanizable fluorocarbon polymers. In particular, among the many and varied copolymers described by Pattison there are specifically disclosed terpolymers derived from tetrafluoroethylene, perfluoromethyl perfluorovinyl ether, and a cure-site monomer of the formula ##STR2## where n is 1 or 2. Pattison discloses vulcanization of these polymers with an aliphatic diamine, generally containing from 2-20 carbon atoms, e.g. p-phenylene diamine, tetramethylamine pentamine, and hexamethylene diamine carbamate.
U.S. Pat. No. 3,580,889, granted May 25, 1971 to Barney and Honsberg, discloses accelerators that can be used to speed the vulcanization of certain fluorinated polymers. Included among the many and varied fluorinated polymers mentioned are polymers derived from tetrafluoroethylene, perfluoro(alkyl vinyl ethers) and perfluoro(2-phenoxypropyl vinyl ether); included among the many and varied vulcanizing agents mentioned is 2,2-bis(4-phenylol) perfluoropropane (i.e. bisphenol AF); and included among the many and varied accelerators mentioned is 2,5,8,15,18,21-hexaoxatricyclo [20.4.0.0.sup.9.14 ] hexacosane (i.e. dicyclohexyl 18-crown-6). In fact the most commonly used vulcanizing agent for the polymers of Pattison is a mixture of bisphenol AF and DCH 18-crown-6.